The present invention relates to a spring clip for holding sheets of paper or the like.
The inventor of the present invention suggested a very useful spring clip as disclosed in Japanese Utility Model Publication No. 3-7177/1991 (corresponding to U.S. Pat. No. 4,991,269 issued Feb. 12, 1991). This conventional spring clip will be explained presently with reference to FIG. 13.
In FIG. 13, the conventional spring clip has a first holding portion 1, a second holding portion 2 in a confronting engageable relation with the first holding portion 1 and a side wall portion 3 joining the first and second holding portions at their middle portion of the longer sides thereof. A slit 4 is formed in the first holding portion 1 so that it extends along the longer side of the first holding portion 1. The first holding portion 1 has a tension strip 5 between the longer side opposite to the side wall portion 3 and the slit 4, a pressing portion 6 at a center thereof and on the opposite side of the tension strip portion 5 relative to the slit 4, and reversing portions 7 at opposite ends.
When the conventional spring clip is used for holding sheets of paper, the sheets of paper are positioned between the spaced two holding portions 1 and 2 with the first holding portion 1 set as indicated by a phantom line A, and then the opposite ends of the reversing portions 7 are pushed by applying forces C and D thereto in the directions shown by arrows so that the reversing portions 7 are reversed or turned over to the state B indicated by a solid line. Thus, the sheets of paper are held in position by the holding portions 1 and 2.
When holding of the papers is required, a spot of the middle of the pressing portion 6 is pushed by applying thereto a force E in the direction of an arrow by manipulation, with the result that the reversing portions 7 are turned over back or returned from the state B to the state A.
The conventional spring clip described above is longitudinal and therefore it has a feature that the papers or the like is less covered up therewith so that less area of the papers is hidden by the clip. However, the inventor of the present invention has found that this conventional spring clip has a problem that, if the width of the pressing portion 6 is made smaller so as to develop the above-described feature more effectively, it causes substantial difficulty in the reversing action of the pressing portion 6 since the dimension F is reduced and consequently moment (E.times.F) becomes smaller.
If, on the other hand, the width of the pressing portion 6 is increased by decreasing the width of the slit 4, it also causes difficulty in the reversing action of the pressing portion 6 due to an increase in rigidity and, in addition, stress concentration is produced in the edge-shaped spots of the opposite end parts of the slit. This causes a phenomenon that the spot are cracked by a stress which is produced repeatedly on the occasion of reversing actions.
Besides, a wave-shaped portion 8 extending outwardly is formed at the middle portion of the tension strip 5 and the wave-shaped portion 8 sometimes interferes a pressing action by a fingertip operation since a fingertip of a user touches accidentally the portion 8 at the time of pressing.
Furthermore, the width of the side wall portion 3 is set at the same medium dimension both on the side of the first holding portion 1 and on the side of the second holding portion so that the side wall portion 3 has the same width along its length as illustrated in FIG. 13, and this causes problems that the first holding portion 1 is not reversed smoothly and that a sufficient holding force is not obtained since the rigidity in the longitudinal direction of the second holding portion 2 is not large enough.